30 nuculida:. 



retusiou. General surface concentrically wrinkled throughout; 

 tlie ribs even, and narrower than their intervals. Sides equal or 

 nearly so ; front one attenuately rounded at its extremity ; hinder 

 one rapidly beaked, its peculiarly prominent tip very acutangular, 

 and rather below than above the middle. Dorsal slopes moderate, 

 at first straightish ; the hinder one eventually incurved and more 

 decided. Ventral margin arcuated, straighter behind, sinuated 

 by the two refusions. Escutcheon large, almost longitudinally 

 wrinkled in the middle, concave at the circumference (where it is 

 lamellately ribbed), and carinately defined by the umbonal ridge, 

 which is subimbricated by the flattened ribs. Hinge-margin 

 broad : teeth not very numerous, rather more in front than behind 

 the extremely minute triangular cartilage-pit. — The types, of this 

 very small, yet distinct, species are preserved in our national col- 

 lection. In one of them the costal intervals exhibit manifest traces 

 of radiating sculpture. The lunule we cannot clearly distinguish. 



50. L. CRISPA, Hinds, f. 107, 108. — T. parva, sequilateralis, 

 ventricosa, subovato-rostrata, antice sulco conspicuo radiata, pos- 

 tice lira interrupta radiante retusionem subitam prsecedente or- 

 nata, liris subinclinatis (quarum interstitia postica sunt clathrata) 

 conceutrice sculpta. Extremitas rostri recurvata, obtuse acumi- 

 nata. Margo dorsalis antice vix declivis ; ventrahs in medio et 

 antice arcuatus. Area magna, rugis arctis concentrice costellata, 

 duplex, inferne profunde excavata. Lunula angusta, lined cir- 

 cumscripta, transversim costellata. — Beaked-subovate, ventricose, 

 gaping at the posterior tip, with a conspicuous broad indented 

 ray in front, and, after a fine interrupted radiating lyra, a fang- 

 shaped abrupt sinking of the surface posteriorly, the concavity of 

 which gives prominence to the umbonal ridge. General surface 

 concentrically costellated throughout ; the riblets somewhat shel- 

 ving, about as broad as their intervals, which are radiatingly ly- 

 rated at the posterior end. Sides equal or very nearly so : anterior 

 extremity tapering, rounded : posterior side beaked, the tip bluntly 

 peaked, recurved, subcentral. Front dorsal slope slight, plano- 

 convex : hinder dorsal slope moderate, at first straightish, abruptly 

 incurved at the termination. Ventral margin arcuated and ex- 

 ternally crenulated in the front and middle, straighter and rising 

 behind, indented before the posterior ridge. Luimle narrow, 

 linearly defined, cross-barred : escutcheon large, with close con- 

 centric flexuous costellar wrinkles, double, the exterior being 

 broadly and deeply excavated. — The only specimen known to me, 

 which now belongs to Mr. Metcalfe, who purchased Mr. Hinds's 

 collection when he quitted England, has no epidermis; its ribs 



